cell biology transcription Flashcards
the expression of genes into proteins involves 2 processes:
transcription and translataion
( the regulation occurs at each step as:
1- chromatin structure
2- transcription initiation
3- mRNA stability
4- trasncriptiing processing )
when cell needs to produce certain proteins , it activates the region of the genome encoding for that protein and produces —- copies of that dna in the form of —–
- multiple
- mRNA
multiple copies of —- are used to translate the genetic code into protein aka the photocopy portion of the cell through the action of the cells protein manufacturing machinery called —-
- mRNA
- ribosomes
—– expands the quantity of a given protein and it gives an important control point for regulating when and how much proteins gets made
mRNA
- important for copying the genetic info from dna ( primary a storage form of the genome )
- contributes to the formation of ribosomes ( ribosomes are particles important for the sythesis of new proteins )
- help assemble new polypeptides by bringing individuals amino acids ( tRNA )
are all fucntions for —–
RNA
rna is — stranded of 2/3degree structure and is found in —— and the sugar is —- while dna is only found in —-
- single stranded
- nucleas and cytoplasm
- ribose sugar
- nucleas
—– is a type of rna that codes for proteins when produced by transcprtion , is translated m contains instruction for protein scythes and is found in nucleus and cytoplasm
mrna
—- is a type of rna that form a basic structure of the ribosome and catalyse protein sythesis
rRNA
—- is a type of rna by which it function in variety of nuclear process including splicing the pre-mrna
snRNA ( small nuclear rna )
—- type of rna that function in variety of diverse cellular process including regulation of gene expression , x- chromosome inactivation and protein transport
ncRNA ( non coding rna)
transcription begins at the —- at the end of the —- region , trancrption ends at the —– site
- transcription start site ( TSS)
- promoter region
- termination site
—- are regions of the dna upstream of the TSS which lead the initiation of transcpriton , each gene has a unique one and the 2 different types are:
- promotors
- basal promotor and enhancer element
—- recognised by the proteins that will aid transcription ( aka transcription factors )
enhancer
— bound by a key transcriptional enzyme rna polymerase II and basal transcription factors required ( which is required for rna pol II bidding )
basal
—– essential for trancpriton of all genes and fucntions recruit in RNA pol II , binds basal/general trancripton factors first and these once are bound to en pol II will bind . example:
- basal promotor
- TATA box which is common ( 20-30 base pairs from transcriptional start site and can bind basal Tfs and RNA pol II )
—- is a process by which the info in a strand of dna is copied into a new molecule of messenger rna ( mRNA )
transcpriton
( process:
1- transcription by which exons are protein coding and introns are non coding
2- trancirption processing
3- splicing
4- protein transaltion )
transcpriton is catalysed by —- which this enzyme transcribes just one of the 2 dna strands of the gene reading the template —- direction and making and rna copy —- direction
it incorporates ——- when creating mrna copy of the dna
- rna polymerase II
- 3’-5’
- 5’-3’
- NTP ( nucletodietriphosphate aka a,g,u,c )
three stages of tracnription :
1- in initiation the —– binds to the dna and unwind 17-18 bp segment of the —–
2- in elongation the —– moves along the — sytheisinf dna until it reaches the ——- . during this phase an area of the dna under the rna poly II remains — this —– moves along the dna
3-in termination the transcription continues beyond the —– , it recruits the —– enzyme that cleaves mRNA which is 20 bases —- beyond the sequence
- rna polymerase II
- promoter aka the open complex
- rna poly ii
- template
- termination region
- unwound
- transcription bubble
- protein encoding region 3’UTR ( untranslated region )
- endonuclease
- downstream
true or false:
in termination most eukaryotic mRNA precursors have the motif AAUAAA within the transcribed sequence = polyadenylation signal sequence
true
in post transcriptionl mrna processing:
the rna molecule sythesies by the rna pol II is called —- and the collection of these precursors molecules is known as —-
extensive modification in:
-primary 1 degree transcript
-heterogeneous nuclear rna ( hnRNA)
- 5’ capping and 3’ poly A tail
—- is the addition of the 6-methyl-guanosine residue .
the function of this capping is the protection of the mRNA from degradation of the exonuclease , promotes nuclear export and aids recognition by the translational machinery
- 5’ capping
after the polyadenylation signal sequence has been —- which is the —- , —- is recruited and cleave —- , then the poly A polymerase then add 40-250 adenine residues to the cleaved —– end
- recognised
- AAUAAA
- endonuclease
- mrna
- 3’end
mRNA from different genes have their longevity encoded within them the — sequence determines the stability of the mRNA and the destabilizing of this sequence target for —— and the — protects from the degradation
- 3’ UTR
- endoculease
- 5’cap
—— confers mRNA stability
poly A tail
gene transcribed to produce mRNA with both — and —-
the —- only encode the protein coding region of the mrna must be processed before translated
- exons and introns
- exons
the main areas of post transcprtional regualtion are:
- mrna stability
- differential mrna splicing
the non coding intronic sequence are not presented in —- they are spliced/cut our and adjacent — are joined together,
- mature rna
- exons
1-the splicing is Carrie out by molecular machine known as —- as its a large complex consisting od ——
2- small nuclear RNA combine w number of proteins to form —- which facilitate splicing by recognising and interacting w specific sequence at each end of the intron , cutting and rejoining the rna
3- splicing occurs releasing the —
- splicisomes
- proteins and rna
- snRNA
- introns
we need to turn genes on and off to genrate —- as every cell has the same dna content bu differentiate into different cells
- specify
—- genes are involved in metabolism/dna repair , regulating transcription and translation and they are always being made
- constitutive gene
—– are only syethsied when required and it determines the development and tissue specificity and allows the cells to respond to the environment as: hormones m cytokines , cell-cell interaction
inducible gene
1- transcpriton can be activated in a —–
2- —- always on and level of gene expression is determined by how many —- and how much — around
3- — turned on when needed and determines the tissue specificity
- constitutive or inducible
- consitive
- binding sites
- tf
- inducible
—- are proteins that bind specific dna sequence in the gene promoter , it controls the — of the transaction , 100s of different transcpriton factors each recognise unique dna sequence , it also interacts w rna pol II
- transaction factors
- rate
the number of —— for the transcrption factor in the promoter region determines the — of the transcprion
- binding sites
- rate
—- allows only genes that are required to be switched on , allows rapid and dynamic response to stimulus , specific regulation of adjoining regions of dna
inducible tf
—– are small strands of rna that regulate dene expression (20-25 nucleotide ) , transcribed from the dna but non coding aka they don’t make proteins , partially complimentary to the number of mRNA aka the protein coding ones , primary function is to down regulate gene expression
microRNA , miRNA
how does miRNA block gene expression ?
1- promotes rna — and binds complementary sequence in the —- UTR which induces degradation
2- binds — and blocks —-
- degradation
- 3’
- mrna
- translation
true or false:
- non coding dna is known as junk dna
- only 2% of human genome makes protien
- 205 is the elements required for gene expression as introns , promoters , enhancers
- true
- false , 1%
- true
